Bone conduction hearing device



April 22, 1941 J. R. CUBERT BONE CONDUCTION HEARING DEVICE Filed Nov.20, 1939 r kwk m J..

INVEN TOR. B J/@J wef lJE Patented Apr. 22, 1941 BONE CONDUCTION HEARINGDEVICE Joseph R. Cubert, Chicago, lll., assignor to Aurex Corporation,Chicago, lll., a corporation of Illinoia Application November 20, 1939,Serial No. 305,277

8 Claims.

'I'his invention relates to what are commonly called piezo-electricdevices, and more particularly to those that are adapted for use as ahearing aid, by deaf people, by using bone conduction, as by placing thedevice against the mastoid bone back of the ear.

Generally stated, the object of the invention is to provide a device ofthis kind in which the crystal, say, of Rochelle salt, is mounted orequipped in a novel and approved manner, thereby to improve theeiilciency and effectiveness of the device.

It-ls also an object to provide certain novel features of constructionand combinations tending to increase the general efficiency anddesirability of devices of this character.

To the foregoing and other useful ends, the invention consists inmatters hereinafter set forth and claimed and shown in' the accompanyingdrawingjin which- Fig. 1 is a perspective of a hearing aid deviceembodying the principles of the invention.

Fig, 2 is an enlarged vertical section on line 2-2 in Fig. 1 of thedrawing.

Fig. 3 is a transverse horizontal section on line 3 4 in Fig. 1 of thedrawing.

Fig. 4 is a perspective of the Rochelle salt crystal employed in saiddevice.

Fig. 5 is a similar perspective view, but showf ing a different form ofthe invention.

Fig. 6 is a diagrammatic view illustrating the action ofthe bender typeof crystal shown and employed in Fig. 2.

Fig. 7 is a similar view illustrating the action of the so-calledtwister type of crystal shown in Fig. 5 of the drawing.

Fig. 8 is a diagrammatic/view of the circuits of the apparatus, of whichsaid device is a part.

As thus illustrated, the invention, as shown in Figs. 1 to 4, inclusive,comprises a Rochelle salt crystal composed preferably of two fiatsections I and 2, held iiatwise together in the well known manner.Preferably, this crystal is of less width than length, and has itsmiddle provided with a weight 3, suitably secured thereto. The ends ofthe crystal have U-shaped springs I secured thereto, in any suitable ordesired manner, as by cement, and the other ends of these springs arethen fastened in any suitable manner to the bottom or back wall 5 of theboxlike housing which encloses the crystal. The top or outer wall 6 maybe removable, if desired.

'I'he lower end of the crystal is provided on its opposite surfaces withflat electrode conductors l and 8, which are in turn connected with thewires 9 and I0 leading to a microphone and amplifier ii, of any suitableor desired character, which in turn is connected to 'the batteryA i2, ofany suitable character, the entire apparatus being made on a smallscale, so that it can be carried around by a deaf person, with the boneconduction piezo-electric device on the head, and with the battery andother elements in agcoat pocket.

It will be seen that the crystal formed by the flat sections i and 2 isof the bender type and that, with its resilient support at its oppositeends, this crystal vibrates at its middle, back and forth, asillustrated in Fig. 6 of the drawing, the weight 3 ensuring the'necessary inertia.

As shown in Fig. 5, the crystal I3 is of the socalled twister type,having springs i4 applied to three of its corners, and having a weightl5 applied to the other corner. With this arrangement, the crystal has atwisting action, instead of just a straight bending action, and vibratesin a twisting manner, as illustrated in Fig. '7 of the drawing. 'I'hecrystal 3 is preferably square, instead of being oblong.

Thus, in each form of the invention, the crystal is, in effect, afloating element,- as it is not held stationary at any point thereon,for to the contrary it is free to vibrate or move throughout its entirearea, as the result of the resilient support provided. This results in atrue and substantially perfect action, so that the vibrations arecorrect, ensuring proper transmission of the sound, und'storted, to theauditory elements within the head of the user, for very often theseinside auditory elements are in normal condition, even though theear-drum or outside elements have become defective.

Therefore, when an alternating electric current is passed through thecrystal, to impose a potential thereon, the vibrations of the crystalare transmitted through the springs to the wall of the box, and throughthis wall to the bone of the head, and thence to the inside auditoryelements.

The characteristics of Rochelle salt crystals are well known and it isquite generally understood that they are distorted when subjected to analternating electric current, and that they generate the current whensubjected to mechanical pressure or distortion Of course, there areother substances, other than Rochelle salt, that can be used to form thecrystal, but in some ways Rochelle salt is preferable.

It will be understood, of course, that these Rochelle salt crystals aresold in the form shown and described with the two sections thereofcemented together, and that the outer fiat Surfaces of the oppositesides of the crystal covered with an extremely fine film of metal, andthat the electrodes are fastened to the said film of metal. The saidmetallic film thus found on commercial crysn tals of this kind is sothin that it cannot be represented by two lines nor even by a very neline, as it is formed by the thinnest kind of metal foil. It merely putsa metallic surface on the crystal, practically Without adding anythingto the thick-- ness thereof. lThis is so well known and underq stoodthat it needs no further explanation.

It will be seen, therefore, that in each form ci the invention there issomething at each corner of the crystal plate thataffects the vibrationof the crystal, and in each form of the invention there is at least onecorner that has such means on only one flat side of the plate, and it isfound that this is of advantage in various ways.

It is important to observe that the vibration affecting means at eachcorner of the crystal plate, in each form of the invention, isunconnected with anything flexible other than the plate itself.

What I claim as my invention is:

1. A piezo-electric bone conduction hearing device having anV electriccurrent input and a mechanical vibration output, comprising a crystalplate of rectangular form, and means attached at each of the fourcorners of the plate, for affecting the vibrations thereof, the means ofat least one corner being all on one side of the plate and separate fromthe means of another corner, and there being at least three cornershaving practically the same kind of means, in combination with a boneconduction member subject to the vibrations of the crystal and adaptedto be placed against the head and forming a support for said crystal,said means comprising spring supports for said three corners, with aweight at the four-th corner.

2. A piezo-electric bone conduction hearing device having an electriccurrent input and a mechanical vibration output, comprising a crystalplate of rectangular form, and means attached at each of the fourcorners of the plate, for affecting the vibrations thereof, the means ofat least one corner being all on one side of the plate and separate fromthe means of another corner, and there being at leastl three cornershaving practically the same kind of means, in combination with a boneconduction member subject to the vibrations of the crystal 'and adaptedto be placed against the head and forming a support for said crystal,the said plate being weighted for vibration,

3. A piezo-electric bone conduction hearing device having an electriccurrent input and a mechanical vibration output, comprising a crystalplate of rectangular form, and means attached at each of thefour cornersof the plate, for

affecting the vibrations thereof, the means of at least one corner beingall on one side of the plate and separate from the means of anothercorner, and there being at least three corners having practically thesame kind of means, in combination with a bone conduction member subjectto the vibrations of the crystal and adapted to be placed against thehead and forming a support for said crystal, said means comprising aspringr support at each of the four corners, and the middle oi' theplate being weighted for' vibration..

e. A piezo-electric bone conduction hearing device having an electriccurrent input and a mechanical vibration output, comprising a crystalplate of rectangular form, and means attached at each of the fourcorners of the plate, for affecting `the vibrations thereof, the meansof at least one corner being all on one side of the plate and separatefrom the means of another corner, and there being at least three cornershaving practically the same kind of means, in combination with a boneconduction member subject to the vibrations of the crystal and adaptedto be placed against the head and forming a support for said crystal,theplate being resiliently supported and weighted for vibration.

5. A structure as specified in claim 4, said plate being a twister witha Weight at one corner thereof.

6. A structure as specified in claim 4, said plate being a bender with asupporting spring at each corner thereof and with a weight carried by.the middle of the plate.

7. In a piezo-electric device for imparting mechanical vibrations to aload, a vibrator comprising a member of piezo-electric crystalsubstance, electrode means for impressing electric oscillations on thepiezo-electric substance of said member to 4produce a vibratory motionof said vibrator, and mechanical springs supporting said vibrator in afloating condition and coupling said vibrator to a load toA causetransfer of vibratory energy produced by said vibratory motion to saidload, said springs being resilient in the direction of the transfer ofthe energy.

8. A piezoLelectric bone conduction hearing device comprising a boneconduction member to be placed against the head, a piezo-electriccrystal, electrode means for impressing electric oscillations on apiezo-electric crystal to produce a vibratory motion, and mechanicalspringssupporting said crystal at opposite edge portions and connectedto said bone conduction member for supporting said crystal in a floatingcondition and coupling said crystal to said bone conduction member tocause -transfer of vibratory energy to said member, and a weightattached to said floating crystal.

JOSEPH R. CUBERT.

